SAN FRANCISCO (CNN) -- She checked herself into a hospital 17 days ago for a bladder infection. But nobody could've predicted it would end like this.
When Lynne Spalding went missing from San Francisco General Hospital, her friends frantically searched and left messages on a Facebook page to keep each other hopeful.
On Tuesday, the messages on the "Find Lynne" Facebook page turned from hope to anger. A body was found in an exterior stairwell of the hospital, and a law enforcement source says it is believed to be Spalding.
How could this be? Spalding's friends had searched throughout San Francisco, in alleys and shelters, handing out hundreds of fliers. They wondered whether the woman, dazed by powerful medication, was wandering around somewhere.
"So we have a lot of questions as her family and friends," said David Perry, a Spalding family spokesman. "Did anyone see her leave the room? Did she leave alone? Is there videotape of Lynne leaving the hospital or wandering the halls?"
All who looked for Spalding, 57, who has two adult children, assumed the hospital had been searched thoroughly.
"Dumbfounded that they didn't find her for two weeks?! Where the hell were they looking?!" Liz Kennedy wrote on the "Find Lynne" website.
"I honestly believe there should be an investigation into how the hospital areas were not thoroughly checked by the staff," another poster named Sunil Raj wrote.
Hospital officials and police say they are investigating. The hospital says it has no idea how the body ended up in the rarely-used staircase.
"We're distressed," Rachael Kagan, a spokeswoman for San Francisco General Hospital, told CNN affiliate KTVU. "We don't know what happened. That's our top priority, is to find that out."
Spalding was last seen in the morning of September 21. Nurses were checking on her every 15 minutes, but at 10:30 a.m., she was gone.
Thirty minutes later, two of her friends and her boyfriend arrived at the hospital to visit, Perry said. They were told that Spalding had been missing for 30 minutes, Perry said.
"Someone has died in a mysterious fashion at San Francisco General Hospital, an institution which is known for healing," Perry said. "And tonight I'm sure the staff of SF General is horrified and confused, certainly the family is horrified and confused."
-- CNN's Lateef Mungin wrote and reported from Atlanta, and Dan Simon reported from San Francisco
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